RE: [PATCH for-next V2 0/9] Add completion timestamping support

[Christoph Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>]

On Thu, 4 Jun 2015, Hefty, Sean wrote:

> If I were adding timestamps, I would probably define a new completion
> structure with 2 u64 time stamp fields (start and end times), and figure
> out when start occurred, end occurred, and the timing metric later.  :)

Not sure why you would need the start. The app knows when it submitted a
send request and incoming packets can be readily timed with taps if
necessary. If you want the start on inbound packets then you have the
challenge that the adapter needs to figure out when the first bit of the
message actually arrived and the timestamp information needs to be pushed
through all the way through the pipeline. Completion is easily done.

> I would assume that these are non-wrapping values.

Its fine what we have now as far as I can tell.

I am not sure why it is necessary to make this more complicated than it is
now. We need a simple means to obtain the completion time and that is what
the current implementation provides. There is even another vendor
(chelsio) who has a similar implementation.

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